Now is definitely the best time to buy - interest rates are at all-time lows. If you can comfortably afford it and are ready to move then I say go for it. I'm not sure what your situation is, but you actually could save some money by waiting a little longer though. Your house will slowly increase in value over the course of a few more years, so you will be able to sell it for more and essentially save money on your new house.However, if you wait, then interest rates may also go back up and you really will not gain anything at all. You just have to weight your pros and cons, do all the math (again, I don't know what your current interest rate is or how rapidly your home value increases), and ask yourself if you are ready to move.
I am surprised that you are able to pay your CURRENT monthly mortgage payments with a mortgage of $130,000 on an annual salary of $50,000. Congratulations - either you or your wife must be a whiz at money management and survival level frugality. If you sell the old house for $335k and pay off the mortgage of $130k the proceeds of the sale will be $205k BEFORE closing costs are deducted. Thats assuming, of course, that you actually get the full asking price of $335k. If you sell the house for less than this and if you incur closing costs of $10k - $15k (mostly real estate commissions) then you receive substantially less than $205k. However, lets assume that you are actually able to put down $200k on the new house, you will still have a mortgage of $200k - on a $50k annual income????? Good luck. And if you only put down $150k you will have a $250k mortgage...again on a $50k income. I don't think so.
If you only make 50k a year, you have NO business buying a house that costs 400k even with your 150k down.You are going to be stretched wwwwwwaaaaaayyyyy too thin! You will be house poor and regret your decision.NO, this plan sucks!
I think you'd still have trouble qualifying for the payment. Even if you can qualify it still doesn't mean that it's a good idea.I think you are rushing it. Save some money for the expenses that will come along with the kids.